About This Calculator
Who builds this, how the numbers are worked out, and why you can rely on them.
Last updated:
What this site is for
Converting between hectares and acres is a small problem that shows up constantly — in property listings, farm paperwork, survey documents and school assignments. Most of the tools that answer it are buried under advertising, demand an email address, or quietly round the result until it is wrong.
This site does one thing: convert land area between hectares and acres, accurately and instantly. There is no account, no advertising interrupting the tool, and no data collection. The calculator runs entirely in your browser, which means the numbers you type are never transmitted anywhere.
Methodology
How we calculate
Both units have exact legal definitions in square metres. A hectare is defined as exactly 10,000 m² — a square 100 metres on each side. The international acre is defined as exactly 4,046.8564224 m², a figure fixed by the 1959 international yard and pound agreement between the United States, United Kingdom, Canada, Australia, New Zealand and South Africa.
We derive the conversion factor from those two definitions rather than hardcoding a rounded constant. Dividing 10,000 by 4,046.8564224 gives 2.4710538146716533 acres per hectare. The calculator carries that full precision through every computation and rounds only at the moment a figure is displayed.
That choice matters more than it sounds. A tool that stores the factor as 2.47105 and multiplies by it will not return your original number when you convert back — the error compounds. Because we round only at display time, converting 137.5 hectares to acres and back returns exactly 137.5.
On precision
Results are shown to six significant figures, matching the precision of the conversion factors we publish. Quoting more digits would imply an accuracy the stated constants do not carry; quoting fewer would make the calculator disagree with the figures printed elsewhere on this site. Six is the number that keeps everything consistent.
The figures we use
- 1 hectare
- 10,000 m² (exact)
- 1 acre
- 4,046.8564224 m² (exact)
- 1 hectare
- 2.47105 acres
- 1 acre
- 0.404686 hectares
- 1 acre
- 43,560 sq ft (exact)
- 100 hectares
- 1 square kilometre
Sources
Where these definitions come from
The hectare is defined by the International Bureau of Weights and Measures as a unit accepted for use with the SI. The international acre derives from the international yard (0.9144 m exactly), agreed in 1959. Neither definition has changed since, which is why the conversion factor is stable and identical worldwide.
Corrections
If you spot a figure that looks wrong, we want to know. Accuracy is the only thing this site offers, so errors get fixed quickly.
Written by
Ali Raza
Founder & Editor, Gem Programmers
Ali Raza builds measurement and conversion tools, and writes about the units people actually run into — in property listings, farm paperwork and survey documents. He founded Gem Programmers, a small studio focused on fast, accurate, ad-free web tools.
Spotted an error? Report it — or write for us.
- Standard conversion (1 ha = 2.47105 ac)
- No login required — 100% free
- Your data never leaves your browser
Use the calculator
Free, instant, works in both directions, and nothing you type leaves your device.